Solenoid with molded plunger guide



Jan. 28, 1964 R. w. BACH! soLENoxD WITH MOLDED PLUNGER GUIDE 3 Sheets-Shea?l 1 Filed April 4, 1961 @MMV Fahr? MEM/zz Jan. 28, 1964' R. w. BACH] 3,119,954

SOLENOID WITH MOLDED PLUNGER GUIDE Filed April 4. 1961 3 Sheets-Sheet 2 0 /a its" S/ a 3/ R. W. BACHI SOLENOID WITH MOLDED PLUNGER GUIDE Jan. 28, 1964 5 Sheets-Sheet 5 Filed April 4, 1961 www Iabz' Wmz gse United States Patent O 3,119,954 SOLENOID WITH MLDED PLUNGER GUIDE Robert W. Bachi, 520 Rush St., Itasca, lll. Filed Apr. 4, 1961, Ser. No. 100,758 9 Claims. (Cl. 317-186) This invention relates to solenoids and refers more particularly to improvements in solenoids intended for alternating current service.

A typical solenoid of the type to which the invention relates has a laminated magnetic frame which is substantially C-shaped or U-shaped as viewed from the side, with the legs of the frame embracing a coil wound upon a hollow bobbin. A magnetic plunger which extends parallel to the legs of the frame is mounted for lengthwise sliding movement between the frame legs, and upon energization of the coil the plunger is of course drawn inwardly of the bobbin, toward the bight portion of the frame.

Heretofore, it has been conventionalr to guidingly support the plunger of such a solenoid on a pair of substantially T-shaped metal guide members which were secured to opposite sides of the frame, usually by means of rivets, and which had inturned lengthwise extending anges that embraced the plunger to support and steady it in its lengthwise motion.

The metal of which such plunger guide members was formed had to be carefully selected not only for its sturdiness but also for its sliding friction characteristics, since the drag of the plunger in the guide members opposed the tractive force exerted by the winding and naturally diminished the work that the solenoid could perform. This prior type of plunger guide posed a more serious objection due to the fact that it had to be secured to the frame by a riveting or staking operation which frequently resulted in distortion of, the frame, with the result that the solenoid became noisy.

By contrast with such prior construction the present invention has for its object the provision of a plunger guide for a solenoid of the character described which may be formed as a unitary member molded of plastic or other material having a low coefficient of sliding friction, and which can be assembled tothe frame of the solenoid without any riveting or staking operation or similar manufacturing procedure requiring skilled labor or specialized equipment.

Another object of this invention resides in the provision of a solenoid of the charactery described having a one-piece molded plastic plunger guide that is biased into engagement with a portion of the frame by spring means reacting between said plunger guide and a bobbin upon which the coil is wound, and wherein the plunger guide is maintained in fixed relation to the frame by its engagement therewith under the force of said biasing means.

Still another object of this invention resides inl the provision of a solenoid of the character described having a molded unitary plunger guide which is securely maintained in assembled relation to the solenoid frame by biasing means which react between the plunger guide and the bobbin upon which the coil is woundy to hold the bobbin and plunger guide engaged with portions of the frame, and wherein a part of the plunger guide cooperates with the bobbin to maintain coaxial relationship between the bobbin and plunger guide whereby smooth, free sliding motion of the plunger is assured.

A further object of this invention resides in the provision of a solenoid of the character described having a one-piece molded plunger guide which may be very readily assembled with the bobbin, frame and plunger of the solenoid by relatively unskilled labor and without the need for any special tools or equpiment, and wherein 3,119,954 Patented Jan. 28, 1964 the plunger guide and bobbin can be readily disassembled from the frame with the aid of a screw driver, to permit inspection, repair or replacement.

Still another object of this invention resides in the provision of a plunger guide for a solenoid of the character described which plunger guide in nowise interferes with the magnetic or electrical characteristics of the solenoid of which it comprises a part, but on the contrary tends to provide improved solenoid performance by reason of the fact that it has a very low sliding friction with the plunger that it guidingly embraces.

It is also an object of this invention to provide, in a solenoid of the character described, biasing means for urging the plunger guide and bobbin in opposite directions, to hold them engaged with portions of the frame, which biasing means also cooperates with the plunger to provide a stop which denes the outer limit of plunger extension and a resilient cushion which absorbs the shock on both the plunger and winding when the plunger is seated under the tractive force of the energized coil.

It will be seen from the foregoing that it is the general object of the present invention to provide a solenoid construction which is cheaper than those heretofore available, comprises few and simple parts which can be assembled with great facility, and tends to afford improved solenoid performance.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

FIGURE l is a perspective view of a solenoid embodying the principles of this invention;

FIGURE 2 is a side elevational view of the solenoid with a portion of the plunger guide cut away and shown in section;

FIGURE 3 is a longitudinal sectional view taken on the plane of the line 3 3 in FIGURE 2, showing the solenoid with its plunger in extended position;

FIGURE 4 is a view similar to FIGURE 3 but showing the solenoid with its plunger retracted;

FIGURE 5 is ya fragmentary sectional view taken on the plane of the line 5 5 in FIGURE 2;

FIGURE 6 is a perspective view of the molded plunger guide which is a -feature of the solenoid of this invention; and

FIGURE 7 is a disassembled perspective View of the solenoid of this invention.

Referring now more particularly to the accompanying drawings in which like numerals designate like parts throughout the several views, the numeral 5 designates generally a solenoid embodying the principles of this invention, which is intended primarily for alternating current operation, and which comprises generally a laminated C-shaped frame 6, the legs 7 of which extend forwardly from its bight portion 9, parallel to one another, and embrace a coil 10 which is wound on a hollow bobbin 11 of insulating material. At their front ends the legs 7 of the frame have extensions 12 which project toward one another and define an opening through which a plunger 13 extends.

The plunger, which is of laminated construction like the frame, may be generally conventional with a straight stern portion 8 which is lengthwise slidable in the hollow bobbin and which extends parallel to the legs 7 of the frame. In this instance the plunger is shown as being of the type that is substantially T-shaped, with a cross head 14 at its front end which cooperates with the front faces of the frame to define air gaps. Shading rings 15 seated in forwardly opening recesses in the front faces of the frame areheld in place by lugs 16 staked out of the frame 'laminations The bobbin 11 upon which the coil lil is wound is substantially conventional in that it has a tubular body portion 17 and disc-like end flanges 1S and 18 which may be formed integrally with the body portion. The axial length of the bobbin is substantially less than the distance between the front face of the bight portion 9 of the frame and the rear faces of the extensions 12, and the bobbin is lseated in the frame with its rear flange 18 engaged with the bight portion and its front flange 1S spaced from the 'extensions 12. The bore 19 through the bobbin is preferably of such size that the plunger stem 8 is received there- `in with substantial clearance on all sides thereof.

The plunger is supported and guided for in and out lengthwise sliding motion in the bobbin bore by means of Va unitary molded plunger guide 4 which is a feature of the solenoid of this invention and which is disposed in the opening between the frame extensions 12. The plunger guide is formed of nylon or any similar readily moldable material which is hard, easily formed, has good electrical insulating properties, and has a low coefficient of friction so as to offer little resistance to sliding motion of the plunger.

As best seen in FIGURES 6 `and 7, the plunger guide 4 comprises fore and aft extending guide elements 20 which guidingly embrace and support the plunger, and transverse locating members 21 which connect the guide elements and which engage behind the extensions 12 on the solenoid frame to hold the plunger guide in place on the frame. The forward portions of the guide elements 20 comprise a pair of channel members 22 which embrace opposite sides of the plunger and which extend through the opening between the frame extensions and project forwardly beyond the front of the frame. The rear portions of the guide elements comprise integral top and bottom channel shaped members 23 which project rearwardly from the locating members 21 to be snugly received in the bore in the bobbin and maintain the bobbin coaxial with the plunger guide, and which likewise embrace and support the plunger. Attention is directed to the fact that the web portions of the rear channel shaped members 23 are flatwise adjacent to the top and bottom surfaces of the plunger stem, while the web portions of the front channel members 22 are located at the sides of the plunger, being disposed in planes normal to the planes of the webs of the rear channel shaped members 23, so that the plunger stem is well supported and guided along a substantial portion of its length despite the fact that it has sliding contact only with the plunger guide.

The transversely extending locating members 21 have forwardly opening pockets or recesses 25 in their front faces in which portions of the frame extensions 12 are received to confine the plunger guide against lateral motion relative to the frame. The sides of these pockets are defined by forwardly projecting shoulder portions 26 which provide inwardly facing opposing abutments that engage the side faces of the frame extensions 12 to thus steady the plunger against sideward displacement. Up and down motion of the plunger guide relative to the frame is prevented by the engagement of the oppositely facing outer surfaces of the llange portions of the front channel members 22 against the opposing inner surfaces of the frame extensions l2 that define the opening through which the plunger extends.

When the bobbin 11 is assembled in the frame, there is, as mentioned above, a space between its front flange 13 and the rear faces of the frame extensions 12, and the depth of the shoulders 26, as measured parallel to the plunger guide axis, is no greater than the width of this space. Hence, when the plunger guide is preassembled into the bobbin, with the rear faces of the locating members 21 abutting the front flange 18 of the bobbin, the bobbin and plunger guide can be readily inserted into the frame from one side thereof. The bobbin and plunger guide are thereafter locked to the frame by biasing means, designated generally by 2S, interposed between their opposing faces and reacting between them to urge the bobbin rearwardly against the bight portion of the frame and the plunger guide forwardly to where the frame extensions are seated in the pockets 25.

For the sake of compactness of both the frame and the plunger guide, the rear face of each frame extension 12 is preferably cut away forwardly at its inner end, to provide la notch 29, and ythe height of the plunger guide is such that its locating members 21 are snugly received in these notches. If the notches 29 are not provided, the legs 7 of the frame must be made correspondingly longer so that the shoulder' portions 25 of the plunger guide will clear the frame extensions 12 as the preassembled guide and bobbin are inserted into the frame. It will be noted that the engagement of the locating members 21 with the oppositely facing surfaces of the notches 29 helps to confine the plunger guide against up and down displacement relative to the frame.

The biasing means 28 by which the bobbin and plunger Iguide vare urged apart to lock them to the frame comprises -generally a pair of E-shaped spring members 30, a pair of E-shaped stop members 31, and a U-shaped retainer 32. In general, the spring members 30 exert biasing forces upon the plunger guide and bobbin; the stop members 31 provide means for cushioning the seating impact of the plunger upon retraction thereof; and the retainer 32 holds the E-shaped members assembled with the frame.

The bight portion 33 of each of the spring members 30 is bent out of ilatness to a substantially W shape so that said members, when interposed between the bobbin `and plunger guide, react between them to urge them in axially opposite directions. The two spring members 30 are edgewise inserted between the plunger guide and bobbin from opposite sides of the frame, with their outer legs 34 straddling the rearwardly projecting channel shaped members 23 of the plunger guide and their center legs 35 projecting between said members 23. The center legs of the spring members 30 provide stops which define the fully extended position of the plunger and which are engageable by laterally outwardly projecting lugs 40` at each side of the plunger, near its rear end, preferably formed integrally with the outermost plunger l-aminations. In applications of the solenoid where its plunger is moved toward its extended position with a large return force, this form of stop has the advantage of providing a substantial cushioning effect, due -to the resilience of the spring member. The spring member also tends to cushion the reaction shock of the coil when the plunger is retracted.

The stop members 31 are formed of lighter spring metal than the spring members 3l), and serve as shims between the plunger guide and bobbin. The stop members are assembled into the solenoid directly in front of the spring members 30, llatwise overlying them, and with their Outer legs -36 straddling the channel shaped members 23 and their center legs 37 projecting between them, similar to the disposition of the spring members. The center legs 37 of the stop members '31 are bent forwardly, out of the plane of the remainder thereof, for cooperation with lugs 41 on the plunger stem, near the front of the plunger. As the plunger approaches its fully retracted position, upon energization of the coil 10, the cen-ter legs 37 of the stop members are engaged by the lugs 41 and are flexed rearwardly, thus cushioning the hammer blow of plunger seating and exerting a small forward force on the plunger which breaks the residual magnetism.

The U-shaped retainer 32 is adapted to be inserted into the frame directly behind the locating members 21 of the plunger guide and directly in front of the stop Imembers 31, with its legs 39 stnaddling the rearwardly projecting channel shaped members 23. It has apertures 42 near the opposite ends of both of i-ts legs which are adapted to receive -tangs 43 on the E-sh-aped stop members 31. The .tangs 43` are struck integrally from each stop member, projecting forwardly ont of the plane thereof, and are so disposed that they are carnmed down fiat against the body of the stop member las the latter is inserted into the frame but spring out into the apertures 42 as soon as the E-shaped member is in place, to securely resist displacement thereof. The spring members 30 have similar tangs 44 struck out of their surfaces, and these, in turn, engage in the apertures in the stop members left by the outward displacement of the tangs 43. When the biasing means is assembled with the frame, the axial biasing force exerted by the spring member 30 holds the tangs 43 rand 44 .firmly seated in the apertures in the adjacent members in which they .are adapted to be received.

Ilhe lugs 40 near the rear of the plunger can readily pass between the rear channel shaped elements A23: on the plunger guide in order to engage the center legs of the spring members 30, as described above. However, to clear the forward lugs 41 on the plunger the forwardly projecting channel shaped elements 22 have their web portions concavely' bowed in cross section, as at 45.

To facilitate assembly, lthe U-shaped retainer 32 is inserted between the plunger guide and bobbin before lany of the E-shaped members 30 and 31 are installed, and of course the plunger stem is inserted axially into the preassembled plunger guide and bobbin before the E-shaped members are slid into place.

It will be apparent that the U-shaped retainer 32 could be omitted if the plunger guide were provided with suitable dimples in the rear faces of the locating members 21, and the tangs 43 and 44 on the E-shaped members were relocated closer to the outer ends of the outer legs of those members to cooperate with such dimples. However, the use of the U-shaped retainer is not particularly undesirable, even though it constitutes an extra part in the assemblage, because it provides a shim which helps to fill the space between the plunger guide and bobbin when the solenoid is assembled and which thus insures that the plunger guide and bobbin will be urged into engagement with the frame parts with a firm biasing force that holds the elements of the solenoid securely assembly. In this connection it will be observed that the bobbin is held coaxial with the plunger guide by the engagement of the rear channel members 23 in its bore and by the flatwise engagement of its rear ange 18 against the front face of the bight portion of the frame. However, it is of n consequence if the bobbin is not perfectly coaxial with the plunger guide because the plunger is supported solely by the guide, and the bore in the bobbin is substantially larger than the plunger stem so that there is no possibility that the plunger will strike the bobbin.

lf for any reason disassembly of the solenoid is desired, the E-shaped members 30 and 31 can be readily withdrawn from the frame by releasing their respective tangs from the dimples in which they are engaged, with the aid of a screwdriver or the like. With the E-shaped members and the U-shaped retainer removed, the plunger guide can be pushed back into the bobbin as far as it will go, and the bobbin-plunger guide subassembly can then be readily moved sidewardly out of the frame.

From the foregoing description, taken together with the accompanying drawings, it will be apparent that this invention provides an alternating current solenoid having a plunger guide which affords good guidance to the plunger without imposing substantial frictional drag thereon, and which is readily formed as a simple unitary molded part and is easily assembled with the bobbin, frame and plunger of the solenoid without the aid of special tools or equipment.

What is claimed as my invention is:

l. In a solenoid of the ltype having a substantially C- shaped magnetic frame with parallel legs extending forwardly from a rear bight portion and with laterally inwardly projecting extensions at the front ends of the legs, a winding wound on a hollow bobbin which is embraced by said legs of the frame and is confined between the bight portion of the frame and said extensions with its axis vparallel to the legs., and a plunger endwise slidable in the bobbin and which extends through the space between said extensions: a .unitary plunger guide having guide elements which extend parallel to the bobbin axis through the space between said extensions and which guidingly yembrace the plunger at opposite sides thereof, and having portions integral with and transverse to said guide elements which extend across the frame ybehind said extensions and have forwardly opening pockets in which portions of said extensions are seated to hold the `plunger guide against lateral and forward displacement; and biasing means reacting between the plunger guidey and the frame to urge the plunger guide forwardly into engagement with said portions of the extensions.

2. The solenoid of claim l, further characterized by the fact that said biasing means is confined between the plunger guide and the front end of the bobbin to urge the bobbin rearwardly into engagement with the bight portion of the frame.

3. The solenoid of claim l, further characterized by cooperating means on the bobbin and plunger guide holding them coaxial with one another.

4. The solenoid of claim l further characterized by integral rearward extensions on the plunger guide which project into the bore in the bobbin to hold the bobbin and plunger guide in coaxial relationship and which embrace the plunger at opposite sides thereof and cooperate with the guide elements in providing guiding support for the plunger.

5. In a solenoid of the type having a substantially C- shaped magnetic frame with parallel legs extending forwardly from a rear bight portion and with laterally inwardly projecting extensions at the front ends of the legs, a winding wound on a hollow bobbin which is embraced by said legs of the frame and is confined between the bight portion of the frame and said extensions with its axis parallel to the legs, and a plunger endwise slidable in the bobbin and which extends through the space between said extensions: a unitary plunger guide comprising (a) guide elements which embrace the plunger at opposite sides thereof to guidingly support the same, and which extend forwardly through the space between the extensions and project rearwardly into the bore in the bobbin to hold the bobbin and plunger guide coaxial, (b) locating elements integral with the guide elements, disposed behind the extensions and providing forwardly facing surfaces engaging rear surfaces of the extensions to hold the plunger guide against forward displacement, and (c) integral opposed laterally facing abutments that cooperate with side surfaces on the frame to hold the plunger guide against lateral displacement relative to the frame; and yielding biasing means reacting between the plunger guide and the bobbin to urge the bobbin rearwardly into engagement with the bight portion of the frame and urge the plunger guide forwardly into engagement with the extensions.

6. The solenoid of claim 5, further characterized by the fact that said plunger guide is formed of moldable plastic material having good electrical insulating characteristics and low sliding friction.

7. In a solenoid having a magnetic frame which is substantially C-shaped as seen from the side, with parallel legs which extend forwardly from a rear bight portion and with laterally inwardly projecting extensions at the front ends of the legs, a winding wound on a hollow bobbin which is embraced by said legs of the frame and is confined between the bight portion of the frame and said extensions with its axis parallel to the legs, and a plunger endWise slidable in the bobbin between retracted and eX- tended positions and which extends through the space between said extensions: a unitary plunger guide comprising abutment portions which extend across the rear faces of said extensions, in opposing engagement with the same, and fore-and-aft extending plunger supporting elements which are integrally connected to said abutment portions and which supportingly and guidingly embrace the plunger at opposite sides thereof, said plunger guide also having integral shoulders at the sides thereof which engage side surfaces of the frame to hold the plunger guide against lateral motion; and means biasing said plunger guide forwardly to maintain said portions thereof engaged with the extensions.

8. The solenoid of claim 7, further characterized by the fact that said plunger supporting elements comprise channel shaped portions of the plunger guide which extend forwardly of the extensions and embrace opposite sides of the plunger, and other channel shaped portions 8 of the plunger guide which extend rearwardly into the bore of the bobbin and cooperate with one another in embracing the plunger, the webs of said other channel shaped portions lying in planes perpendicular to those of the rst designated channel shaped portions.

9. The solenoid of claim 8, further characterized by the fact that said means biasing the plunger guide forwardly comprises a substantially E-shaped spring member having its outer legs straddling said other channel shaped portions of the plunger guide and its center leg projecting between them, and having its bight portion bent out of atness to react between the plunger guide and bobbin; and further characterized by an abutment on the plunger engageable with the center leg of said spring member to define one of the positions of the plunger.

References Cited in the tile of this patent UNITED STATES PATENTS 2,338,775 Martin Ian. 11, 1944 2,692,354 Fisher Oct. 19, 1954 2,692,964 Soreng et al, Oct. 26, 1954 

1. IN A SOLENOID OF THE TYPE HAVING A SUBSTANTIALLY CSHAPED MAGNETIC FRAME WITH PARALLEL LEGS EXTENDING FORWARDLY FROM A REAR BIGHT PORTION AND WITH LATERALLY INWARDLY PROJECTING EXTENSIONS AT THE FRONT ENDS OF THE LEGS, A WINDING WOUND ON A HOLLOW BOBBIN WHICH IS EMBRACED BY SAID LEGS OF THE FRAME AND IS CONFINED BETWEEN THE BIGHT PORTION OF THE FRAME AND SAID EXTENSIONS WITH ITS AXIS PARALLEL TO THE LEGS, AND A PLUNGER ENDWISE SLIDABLE IN THE BOBBIN AND WHICH EXTENDS THROUGH THE SPACE BETWEEN SAID EXTENSIONS: A UNITARY PLUNGER GUIDE HAVING GUIDE ELEMENTS WHICH EXTEND PARALLEL TO THE BOBBIN AXIS THROUGH THE SPACE BETWEEN SAID EXTENSIONS AND WHICH GUIDINGLY EMBRACE THE PLUNGER AT OPPOSITE SIDES THEREOF, AND HAVING PORTIONS INTEGRAL WITH AND TRANSVERSE TO SAID GUIDE ELEMENTS WHICH EXTEND ACROSS THE FRAME BEHIND SAID EXTENSIONS AND HAVE FORWARDLY OPENING POCKETS IN WHICH PORTIONS OF SAID EXTENSIONS ARE SEATED TO HOLD THE PLUNGER GUIDE AGAINST LATERAL AND FORWARD DISPLACEMENT; AND BIASING MEANS REACTING BETWEEN THE PLUNGER GUIDE AND THE FRAME TO URGE THE PLUNGER GUIDE FORWARDLY INTO ENGAGEMENT WITH SAID PORTIONS OF THE EXTENSIONS. 